CODEWITHSUNDEEP
r
VBo
VBo

Reputation: 119

applying command on multiple columns of each element of a list

I have a list with 16 elements all having the same variables (31 columns). Now i want to make a few changes on this variables and hope that I can do them for each element of the list. Simplified the list looks like this

>list
>$`M2_2004` 
>       A      B      C 
>1      2      1      3 
>2      4      6      5 
>3      6      4      0 
... 

>$`M2_2005` 
>      A       B      C 
>70    5       9      1 
>71    4       6      5 
>72    2       5      8 
...

For example, now i want to add 2 leading numbers to the columns B and C for each element of the list. This works with the following command

sprintf("%04d", B)

where B is the column. Since I am quite new to R, I would apply this to each column of each element with a seperate line of code, but i hope to speed up the process by doing this in a single command.

Upvotes: 1

Views: 45

Answers (1)

Maël
Maël

Reputation: 51974

You can use lapply to apply the same function to each element of a list, and sapply to apply the same function to multiple columns of the same data frame:

lapply(your_list, function(x){
  x[c("B", "C")] <- sapply(x[c("B", "C")], function(y) sprintf("%04d", y))
})

Upvotes: 1

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